爆破开采诱发周边岩体损伤破裂的数值模拟研究

Numerical Study on Damage and Fracture Degree of Rock Mass Induced by Blasting Mining

基于连续-非连续单元方法（CDEM）中的朗道点火爆炸模型及拉剪复合应变软化模型,探讨了爆破开采与炮孔周边岩体损伤破裂程度的对应关系。通过量纲分析,确定了爆破诱发岩体损伤破裂的主要影响因素;通过应变软化的Mohr-Coulomb模型及最大拉应力模型,详细探讨了不同黏聚力及抗拉强度下,炮孔周边岩体的损伤因子随爆破距离的变化规律。数值计算结果表明：炮孔附近以压剪破坏为主,岩体处于完全损伤状态,出现具有一定半径的密集破碎带;在远离炮孔的区域,以张拉破坏为主,出现若干条贯通性的张拉裂缝;损伤因子随爆破距离的增加呈指数型衰减,并拟合获得了损伤因子与无量纲爆破距离、无量纲黏聚力及无量纲抗拉强度间的函数关系;强损伤区（损伤因子大于0.9的区域）的临界半径一般在2.5～5.5 m,仅受黏聚力控制;弱损伤区（损伤因子小于0.1的区域）的临界半径一般大于8 m,受黏聚力及抗拉强度的联合控制。

Based on Landau firing blasting model and strain softening shear tensile composite constitutive model in Continuum-discontinuum Element Method（ CDEM）,the relationship between blasting mining and damage fracture degree of rock mass surrounding the bore hole is discussed. According to dimensional analysis,the major influence factors related to the damage and fracture process of rock mass under blasting load are determined. By adopting Mohr-Coulomb model and maximal tensile stress model considering strain softening effect,the relationship between damage factors of rock mass and blasting distance under different cohesion and tensile strength is studied. Numerical results show that,a dense fracture zone with compressive shear failure appears near the bore hole,and the rock mass in this zone is totally damaged. In the area far from the hole,the major failure pattern is tensile failure,and some straight tensile fractures appear in this area. With the increase of blasting distance,the damage factor decreases gradually with decaying exponential pattern,and the fitting function between damage factor and dimensionless blasting distance,dimensionless cohesion and dimensionless tensile strength is obtained. The critical radius of strong damage region（ the area damage factor greater than 0. 9） varies about from 2. 5 m to 5. 5 m,only controlled by cohesion. The critical radius of weak damage region（ the area damage factor less than 0. 1） is generally greater than 8 m,and controlled by cohesion and tensile strength.